This invention relates to the manufacture of electrical circuit components adapted to be connected to hybrid circuitry or other flat conductive circuits and, more particularly, to a selectively-coated carrier plate for a miniature transformer and a method of manufacturing same.
Electrical components adapted to be connected to hybrid circuitry are typically mounted on one face of a carrier plate that has wraparound terminal pads leading from the component to the other face of the carrier plate, where the component is electrically connected to flat conductors of a hybrid circuit or the like by solder reflow or a conductive epoxy laydown or the like.
In the case of an inductor, which has only two leads, the fabrication of two appropriate wraparound terminal pads for these leads is a relatively simple matter. Using an electrically conductive paste, conductive strips are formed along opposite sides of each mounting face of a thin rectangular carrier plate by silk screening techniques. After baking the strips, a plurality of these carrier plates are stacked face-to-face so one edge face of each plate between strips adjoins the next. After working a conductive paste into a thin uniform layer on a roller, the layer is transferred to the adjoining edge faces of the plates to electrically interconnect the strips on opposite faces and thereby complete one wraparound terminal pad on all the stacked plates. The other wraparound terminal pad on all the stacked plates is formed in the same way.
In the case of a transformer, which has four, six, or even more leads, wraparound terminal pads cannot be formed by stacking the carrier plates in the same manner as inductors, described above. However, the formation of four or more mutually isolated conductive layers on the edge faces between mounting faces of each carrier plate individually would be extremely time consuming and thus costly.